This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of the proposed project is to identify receptors and other molecules involved in infection by feline immunodeficiency virus (FIV) as well as cell markers recognized by monoclonal antibodies raised in response to immunization with the virus.